This is for my 77 45. It's been using an aux tank in the bed but I'd like to ditch that setup. I had originally bought a new 77 40 tank only to realize that it was just too big for the 45. So now I have a tank from what I believe to be a 64 40. It has the threaded fuel line port on the side etc. Anyway, which fuel sender would I need for this? Would the 64 fuel sender work with my current 77 guage, or is it possible that a 77 sender would work in the older tank ... or did I simply swap one problem for another?